Mathematica

Here is the place you can go to get your very own Mathematica Player: http://www.wolfram.com/products/player/

Here is a link to many of the Calculus demonstrations on Wolfram's Demonstration project:
http://demonstrations.wolfram.com/education.html?edutag=High+School+Calculus+and+Analytic+Geometry&limit=20

And some important ones ... when I get them
(Note - you'll have to download these to run on your version of Mathematica Player (above))

Some demonstrations that illustrate the limit ideas (from the demonstration project):
http://demonstrations.wolfram.com/FiniteLimitAtAFinitePoint/
http://demonstrations.wolfram.com/InfiniteLimitAtAFinitePoint/
http://demonstrations.wolfram.com/FiniteLimitAtInfinity/
http://demonstrations.wolfram.com/InfiniteLimitAtInfinity/

http://demonstrations.wolfram.com/ACaseOfTheEpsilonDeltaDefinitionOfALimit/
http://demonstrations.wolfram.com/LimitLaws/
http://demonstrations.wolfram.com/Discontinuity/